Nitrous is great if the system is engineered correctly and used sensibly.
I've looked at the links posted for nitrous installation and they pose one serious problem: an uncorrected air fuel ratio when the nitros is activated.
This will make the motor run lean, overheat and if used in long bursts, cease the engine or damage the roller bearings if over revved.
To use nitrous you must have a method of adding extra fuel to the airstream to maintain correct air/fuel ratio.
Nitrous used in the right way is great, giving small engines a bit more power when it's needed, like climbing a hill.
If the engine makes 2 horsepower at 3500 rpm or it makes 2.5 horsepower at 2500 rpm with nitrous, the overall load on the engine is not significantly increased.
Scenario: you are approaching a hill doing 25 miles an hour. You know that the bike wont make it up the hill without pedalling.
When the bike speed falls to 20 miles an hour, you hit the nitrous button and maintain 20 miles an hour.
The engine has not been over revved, it didn't destroy itself and it will happily take another shot of nitrous with a corrected air/fuel ratio.
Scenario 2: You are going down a hill doing 35 miles an hour - you hit nitrous with an uncorrected air/fuel ratio and the bike gets to 45 miles an hour and BOOM the engine either blows the bottom end bearing or ceases the top end or both together.
Now you blame the nitrous for blowing up your engine.
Someone in scenario 2 has just made a fool of themselves, then they advise everyone else that nitrous blows up your engine.
I intend to fit nitrous to my bike, but it will be a well engineered system with a electric fuel pump coupled to a fuel injector supplying extra fuel when the nitrous is injected.
Fabian